Compressor motor cooling arrangement for reversible refrigeration system



Oct. 31, 1961 KOOIKER 3,006,163

P. l. COMPRESSOR MOTOR COOLING ARRANGEMENT FOR REVERSIBLE REFRIGERATION SYSTEM Filed Sept. 29, 1960 INVEN TOR. PAU I. KOOIKER HlS ATTORNEY 3,@06,l63 Patented Oct. 31, 1&6}

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COMPRESSOR MOTOR COOLING ARRANGE- MENT FOR REVERSIBLE REFRIGERATKON SYTEM Panl I. Kooiirer, Lyndon, Ky, assignor to General Electric Company, a corporation of New York Filed Sept. 29, 196%, Ser. No. 59AM 5 (Iiaims. (Ci. 62-324) The present invention relates to a reversi le refrigeration system for an air conditioning unit adapted for heating or cooling an enclosure and more particularly to a reversible refrigeration system utilizin a compressor of the type commonly known as a high side case in which the high pressure discharge gases issuing from the compressor are passed into the compressor case for cooling the motor.

It is common practice in the field of refrigeration to mount both the refrigerant compressor and its drive motor within a hermetically sealed casing. In such an arrangement, it is necessary to devise some means for cooling the drive motor in order to maintain its temperature within safe operating limits. One means employed for this purpose is to pass the high pressure discharge gas from the compressor unit over the compressor motor after this high pressure gas has been cooled to a low enough temperature to remove heat from the motor thereby maintaining the motor at a safe operating temperature. The heat removed from the motor is carried off by the gas and dissipated in the condenser of the refrigerating system. This is an efiicient method of maintaining the motor at a proper operating temperature but requires that the high pressure discharge gas be pro-cooled before being passed into intimate contact with the motor. One means devised for cooling the high pressure discharge gas incorporates the injection of condensed refrigerant from the condenser of the refrigerating sysem into the hermetic casing Where it mixes with the high pressure discharge gas to cool this gas and thereby cool the motor. However, in order to withdraw condensed refrigerant from the condenser into the compressor case, it is necessary to overcome the pressure drop in the system which occurs in the condenser and refrigerant tubing leading thereto. It is also desirable to provide some means for automatically increasing and decreasing the amount of condensed refrigerant being added to the case according to the load of the motor, which is normally relatively great when large quantities of gas are pumped and correspondingly less when lesser quantities of gas are pumped.

An injection cooling arrangement of the above type is disclosed in the invention of the application of James L. Schulze, Serial No. 860,848, filed December 21, 1959, now Patent No. 2,967,410, dated January 10, 1961, and assigned to General Electric Company, the assignee of the present application. The present invention is an improvement over the Schulze invention, which invention was made by the said James L. Schulze prior to the present invention. There is no intention to claim as the present invention anything shown or described in said Schulze application, which is to be regarded as prior art with respect to the present application. A difficulty encountered when applying an injection type cooling arrangement to a reversible type refrigeration system, is that the condensed refrigerant is not always found in the same portion of the system. That is, during the summer, when the unit is operating on a cooling cycle, the condensed liquid refrigerant is available at the outdoor heat exchanger, while in the winter, when the unit is usually operating on the heating cycle to provide heat for an enclosure, the source of condensed refrigerant is at the indoor heat exchanger. Thus, in order to supply condenscd refrigerant for injection into the hermetic compressor case, it is necessary to devise some meansfor always assuring that condensed liquid refrigerant will be available for injection to the motor regardless of the direction of operation of the system.

Accordingly, it is an object of the present invention to provide an improved arrangement in a reversible refrigeration system for introducing condensed refrigerant into the discharge gas stream being directed into the hermetic compressor casing for cooling the motor of the motorcompressor unit.

It is another object of the present invention to provide an improved arrangement in a reversible refrigeration system which automatically adjusts itself to provide condensed refrigerant for injection into the hermetic motor casing regardless of the direction of flow of refrigerant through the system.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In accordance with the present invention there is pro= vided a reversible refrigeration system for an air con= ditioning unit adapted for heating and cooling an enclosure including 'a motor-compressor unit sealed within a hermetic casing and connected in reversible re frigerant flow relationship within a pair of heat exchangers. Completing the refrigerant circuit is an expansion means connected between the heat exchanger for expanding refrigerant from condenser pressure to evap' orator pressure as it flows in either direction through the system. A discharge passage leads from the compressor into the hermetic casing for conducting high pressure discharge gas from the compressor into the casing for cooling the motor of the unit. A portion of thisdischargc passage takes the form of an aspirating means, such as a venturi or a jet pump, which means create a region of lower pressure in the high pressure gas flowing through the passage. A bypass tube is connectd in parallel with the expansion means between the heat exchangers so that one of its opposite ends always communicates with condensed refrigerant in the heat exchanger being operated as a condenser. Connecting. at some intermediate point on this tube is a liquid refrigerant conduit which communicates at its opposite end with the low pressure region of the aspirating means. The low pressure region in the aspirating means provides the requisite pressure drop needed to promote flow of liquid refrigerant from the heat exchanger operating as a condenser into the low pressure region where it mixes with the high pressure gas flowing therethrough. On opposite sides of the connecting point between the refrigerant bypass tube and refrigerantconduitleading to the aspirating means are check valve means each operable to permit flow of liquid refrigerant through the tube in the direction of the refrigerant conduit leading to the aspirating means but not in the direction away from the refrigerant conduit. As a further aspect of the in-- vention, the refrigerant bypass tube is provided with suitable restricting mcans on opposite sides of the refrigerant conduit leading to the aspirating means' which restricting means adjusts to the flow of liquid refrigerant to the refrigerant conduit according to the cooling requirements of the motor during the respective cycles of operation of the system.

For a better understanding of the" invention reference may be had to the accompanying drawing the single fig.- ure of which illustrates in somewhat schematic form a reversible refrigeration system incorporating the resent invention.

Referring now to the drawing, there is shown a reversible cycle refrigeration'systenr for use in an air conditioner of the type adapted to both heat and cool air from an enclosure. For compressing and pumping refrigerant through the system there is provided a motor-compressor unit, generally designated by the reference numeral 2. The motor-compressor unit is mounted in a hermetically sealed casing 3 which houses the compressor 4 and its drive motor 6 and which is suitable for containing the high pressure refrigerant gas. A suction line 7 connects directly with the suction inlet of the compressor and carries low pressure refrigerant gas to the compressor. A discharge line 8 is connected to the case for carrying the high pressure gas from within the case into the remaining portions of the system. The discharge and suction lines are both connected to a reversing valve 9. Also connected to the reversing valve 9 are a pair of conduits 11 and 12 which lead respectively to the indoor and outdoor heat exchangers or coils 13 and 14. In an air conditioning unit of this type, the indoor coil 13 is arranged for heating or cooling air fromthe enclosure while the outdoor coil 14 is arranged for either rejecting heat to or extracting heat from the outside atmosphere.

The reversing valve 9 is selectively reversible to direct discharge gas into either one of the lines 11 and 12 while receiving low pressure gas from the other line, thereby making the system reversible for either heating or cooling an enclosure. Thus, if it is desirable to set the system on the heating cycle, the compressor discharge gas flowing through the discharge line 8 is connected by means of the reversing valve 9 to the line 11 which carries the hot discharge gas to the indoor coil 13. This coil then acts as a condenser to give up its heat to the enclosure air. If it is desired to set the system for cooling the enclosure, the suction line 7 is connected through the line 11 to the indoor coil 13, which then acts as an evaporator, while the discharge gas is carried to the outdoor coil 14 by the line 12.

Included in the system for the purpose of expanding the refrigerant from condenser pressure to evaporator pressure is a main refrigerant expansion means or main capillary tube 16. This tube operates as an expansion means during both the cooling and heating cycles and maintains a pressure differential between the evaporator and the condenser regardless of the direction of refrigerant flow.

During operation of the compressor, low pressure refrigerant is Withdrawn from the suction line 7 which connects with the suction port (not shown) of the compressor unit 6. The refrigerant gas is compressed within the compressor unit to a relatively high pressure and temperature and is then discharged by the compressor through a suitable discharge passage 17 leading into the hermetic casing 3. For purposes of illustration, the dis charge passage 17 is shown as a tube leading out of the hermetic casing and then back into the hermetic casing. However, this discharge passage could be a passage, such as that illustrated in the aforementioned Schulze application, which leads from the discharge port of the compressor unit directly into the hermetic casing 6 without leaving the hermetic case. Included within the discharge passage is an aspirating means or venturi section, general-ly designated by the reference numeral 21, through which the hot discharge gas must pass prior to entering the hermetic case. After flowing upwardly over the motor 6, the high pressure gas is conducted out of the casing through the conduit 8 into the remaining portions of the system.

In order to cool the discharge gas flowing through the discharge passage sufiiciently to maintain the motor within safe operating temperatures, cool liquid refrigerant from the heat exchanger operating as a condenser is introduced into this gas as it flows through the aspirating means. As may be seen in the drawing, the aspirating means contains a nozzle or gas accelerating section 22 and a difiuser or gas decelerating section 23 separated by a pinched or throat portion 24. As the high pressure gas flows through the aspirating means, it drops in pressure in the nozzle section 22 where its velocity is increased. Then, in the diffuser section 23 the gas pressure increases to approximately its original pressure as the velocity of the gas decreases. Thus, a pressure drop or region of low pressure is created in the throat 24 of the aspirating means which is easily suflicient to overcome the pressure drop encountered in the case and tubing of one or the other of the heat exchangers. That is, the pressure in the throat 24 is less than the pressure in the latter stages of whichever heat exchanger is operating as a condenser thereby causing liquid or condensed refrigerant to be syphoned through a liquid refrigerant supply conduit 26 which communicates with the throat of the aspirating means. The condensed refrigerant is then mixed with the high pressure gas flowing through the discharge passage 17 and is carried by the high pressure gas into the hermetic casing 3.

Liquid refrigerant, flowing through the conduit 26, is supplied from either heat exchanger 13 or 14 by means of a liquid refrigerant bypass passage or tube 27 that is connected between the heat exchangers 13 and 14 in parallel with the expansion means or capillary 16. The conduit 26 connects with the bypass tube 27 at some intermediate point between the two heat exchangers. A pair of check valves 28 and 29, arranged respectively on 0pposite sides of the connecting point between the refrigerant bypass tube 27 and the condensed refrigerant supply conduit 26, prevent the flow of refrigerant completely through the tube 27 in a direction away from the supply conduit 26. During operation of the reversible cycle refrigeration system, refrigerant is permitted to flow through the check valve adjacent the heat exchanger operating as a condenser but is prevented from flowing through the check valve adjacent the heat exchanger operating as an evaporator. The check valves 28 and 29 prevent short circuiting or shunting of liquid around the main capillary or expansion means 16 from one heat exchanger to the other yet always supply liquid refrigerant to that portion of the bypass passage 27 connecting with the liquid suppiy conduit 26, regardless of the direction of refrigerant flow through the system.

Liquid refrigerant flowing through the bypass passage 27 from heat exchanger 13 is restricted to some extent by a restricting means or first capillary 30. Liquid refrigerant flowing through the bypass passage 27 from heat exchanger 14 is restricted to some extent by a second capillary 31. The capillaries 30 and 31 are arranged respectively between the check valves 29 and 28 and the inlet to the refrigerant conduit 26. It is conceived that the capillary 30 will provide optimum flow for motor cooling purposes during the heating operation of the system while the capillary 31 will provide optimum flow of liquid refrigerant for rnotor cooling purposes during the cooling operation of the system. In the illustrated embodiment of the invention, capillary 31 is shown longer than capillary 30 to indicate that capillary 31 provides greater restriction to refrigerant flow than does capillary 30. Thus, in the ilustrated embodiment of the invention, greater restriction to flow through the bypass passage is provided during cooling cycle operation of the system than during the heating cycle operation thereof. It is conceivable, however, due to certain characteristics of parameters of the particular refrigeration system, that greater restriction in the bypass 27 would be desirable during the winter or heating operation than during the cooling operation. Therefore, the present invention is not limited to an arrangement wherein greater restriction is applied during the cooling operation than during the heating operation. The design of the capillaries 30 and 31 should merely be such as to permit enough condensed refrigerant to flow into the conduit 26 to sufiiciently cool the discharge gas during either cycle of operation of the system but still limit the flow sufliciently to prevent short circuit ing of the evaporator and eventual collection of the refrigerant in liquid form vu'thin the case. Obviously, capillaries do not have to be used for this purpose. Other means such as needle valves or other type of restricting means could easily be substituted for the first and second capillaries 30 and 31.

When the liquid refrigerant is introduced into the throat or low pressure region of the aspirating means, it encounters the hot discharge gases and is vaporized or flashed into gaseous form. Heat removed from the discharge gas, in vaporizing the liquid refrigerant, reduces the temperature of the discharge gas and the violent reaction created by the flashing of the liquid into vaporized form completely m xes the gases so that the resultant gas mixture issuing from the passage is at a uniform temperature and much cooler than the temperature of the original high pressure gas discharged from the compressor.

In operation, the venturi section or aspir-ating means 21 acts as a modulating device for supplying greater or lesser amounts of condensed refrigerant to cool the high pressure discharge gas according to the flow or" gas through the discharge passage from the compressor unit. Since the amount of liquid refrigerant flowing through the supply conduit 26 depends to a great extent upon the pres sure recovery experienced in the diffuser section from throat 2 5 to the outlet of the diffuser and, since the amount of pressure recovery in the venturi or aspirating means is a function of the quantity of gas flowing therethrough, it is apparent that the amount of liquid refrigerant syphoned through the liquid refrigerant supply conduit 26 depends upon the quantity of discharge gas flowing through the discharge passage 1'7 leading from the compressor unit. Whenever the pressure of the suction gas is high, the temperature of this gas at the discharge outlet of the compressor 6 is, under normal conditions, relatively high and the cooling requirement is, therefore, substantial. It is to be noted, however, that when the suction pressure is high, a correspondingly large quantity of gas is pumped which results in a relatively great flow of liquid refrigerant through the passage and through the throat 24 thereby resulting in a relatively large flow of liquid refrigerant through the conduit 26 and, thus, supplying the necessary cooling of the high temperature discharge gas. Conversely, whenever the suction pressure is low and the compressor discharge gas is at a relatively low temperature, the amount of gas being pumped through the discharge passage 17 is correspondingly less. This consequently produces a correspondingly smaller pressure difference between the throat 2d and the outlet of the aspirating means, thereby resulting in a diminished flow through the conduit 26 and a lesser amount of cooling of the discharge gas. Thus, under normal conditions of operating, the aspirating means automatically modulates the amount of cooling of the discharge gas from the compressor, and automatically increases or decreases the cooling effect on this gas to maintain the motor within safe operating limits.

By the present invention there has been provided a cooling arrangement utilizing injection of condensed refrigerant into the high pressure discharge gases issuing into the case of a hermetically sealed compressor in which the condensed refrigerant is made available to the injection means regardless of the direction of flow of refrigerant through the heat pump system. Moreover, this supply of condensed liquid refrigerant is automatically made available by the pressure differentials existing in the system itself as a result of the direction of operation of the system.

While in accordance with the patent statutes there has been described what at present is considered to be the preferred embodiment of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein Without departing from the invention, and it is, therefore, the aim of 6 the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure comprising a motor-compressor unit and a pair of heat exchangers connected in reversible refrigerant flow relationship, expansion means connected between said heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure, means for reversing the flow of refrigerant through said system thereby to operate each of said heat exchangers interchangeably as a condenser or as an evaporator, said motor-compressor unit being mounted in a hermetically sealed casing for containing a high pressure refrigerant gas, a discharge passage leading from said compressor of said unit into said hermetic casing for conducting compressed refrigerant gas from said compressor into said casing for cooling said motor, said discharge passage including an aspirating means for creating a low pressure region in said discharge gas stream as said gas passes through said aspirating means, a refrigerant bypass tube connecting between said heat exchangers in parallel with said expansion means, a liquid refrigerant supply conduit connecting at one end with said refrigerant bypass tube and at the other end with said low pressure region of said aspirating means for introducing liquid refrigerant into said discharge passage so that said high pressure discharge gas flowing into said casing and over said motor is mixed with and cooled by said liquid refrigerant to maintain said motor temperature within safe operation conditions, and check valve means in said refrigerant bypass tube on opposite sides of said connection with said condensed refrigerant supply conduit for preventing flow of liquid refrigerant through said tube in the direction of said heat exchanger being operated as an evaporator during either cycle of operation of said system.

2. A reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure comprising a motor-compressor unit and a pair of heat exchangers connected in reversible refrigerant flow relationship, expansion means connected between said heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure, means for reversing the flow of refrigerant through said system thereby to operate each of said heat exchangers interchangeably as a condenser or as an evaporator, said motor-compressor unit being mounted in a hermetically sealed casing for containing a high pressure refrigerant gas, a discharge passage leading from said compressor into said hermetic casing for conducting compressed refrigerant gas from said compressor into said casing for cooling said motor, said discharge passage including a throat of reduced crosssectional area for creating a low pressure region in said discharge gas as it passes through said throat, a refrigerant bypass tube connecting between said heat exchangers in parallel with said expansion means, a liquid refrigerant supply conduit connecting at one end. with said refrigerant bypass tube and at the other end with said throat of said discharge passage for introducing condensed refrigerant into said throat of said discharge pass-age so that said high pressure discharge gas flowing into said casing and over said motor is mixed with and cooled by said liquid refrigerant to maintain said motor temperature Within safe operating conditions, and a pair of check valves in said refrigerant bypass tube, said check valves being arranged respectively on opposite sides of said connection with said liquid refrigerant supply conduit for preventing flow of liquid refrigerant through said tube in the direction of said heat exchanger being operated as an evapo rator during either cycle of operation of said system.

3. A reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure comprising a motor-compressor unit and a pair of heat exchangers connected in reversible refrigerant fiow relationship, expansion means connected between said heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure, means for reversing the flow of refrigerant through said system thereby to operate each of said heat exchangers interchangeably as a condenser or as an evaporator, said motor-compressor unit being mounted in a hermetically sealed casing for containing a high pressure refrigerant gas, a discharge passage leading from said compressor into said hermetic casing for conducting compressed refrigerant gas from said compressor into said casing for cooling said motor, said discharge passage including a throat of reduced crosssectional area for creating a low pressure region in said discharge gas as it passes through said throat, a refrigerant bypass tube connected between said heat exchangers in parallel with said main expwsion means, a liquid refrigcrant supply conduit connecting at one end with said refrigerant bypass tube and at the other end with said throat of said discharge passage for introducing condensed refrigerant into said throat of said discharge passage so that high pressure discharge gas flowing into said casing and over said motor is mixed with and cooled by said liquid refrigerant to maintain said motor temperature within safe operating conditions, a pair of check valvm in said refrigerant bypass tube, said check valves being arranged on opposite sides of said connection with said liquid refrigerant supply conduit for preventing flow of liquid refrigerant through said tube in the direction of said heat exchanger being operated as an evaporator during either cycle of operation of said system, and a pair of refrigerant restriction means formed in said bypass tube between its connecting point with said supply conduit and each of said check valves for limiting the How of liquid refrigerant through said bypass tube into said refrigerant conduit toward said aspirating means and preventing short eircuiting of said refrigerant around said heat exchanger operating as an evaporator.

4. A reversible refrigeration system for an air conditioning unit adapted for heating and cooling an enclosure comprising a motor-compressor unit and an indoor heat exchanger and an outdoor heat exchanger connected in reversible refrigerant flow relationship, a main expansion means connected between said heat exchangers for expanding refrigerant from condenser pressure to evaporator pressure, means for reversing the flow of refrigerant through said system and thereby to operate each of said heat exchangers interchangeably as a condenser or as an evaporator, said motor-compressor unit being mounted in a hermetically sealed casing for containing a high pressure refrigerant gas, a discharge passage leading from said compressor of said unit into said hermetic casing for con ducting compressed refrigerant gas from said compressor into said casing for cooling said motor, said discharge passage including an aspirating means for creating a low pressure region in said discharge gas stream as said gas passes through said aspirating means, a refrigerant bypass tube connected between said indoor and outdoor heat exchangers in parallel with said expansion means, a liquid refrigerant supply conduit connecting at one end with said refrigerant bypass tube and at the other end with said low pressure region of said aspirating means for introducing liquid refrigerant into said discharge passage so that said high pressure discharge gas flowing into said casing and over said motor is mixed with and cooled by said liquid refrigerant to maintain said motor temperature within safe operating conditions, a pair of check valves, one of said check valves being disposed in said bypass passage between said indoor heat exchanger and said connection with said refrigerant supply conduit and the other check valve being disposed in said bypass passage between said outdoor heat exchanger and said connection with said liquid refrigerant supply conduit, said check valves preventing flow of liquid refrigerant through said bypass tube in the direction of said heat exchanger being operated as an evaporator during either cycle of operation of said system, a first refrigerant restriction means positioned in said refrigerant bypass tube between said inlet to said refrigerant supply conduit and said check valve adjacent said indoor heat exchanger, a second refrigerant restriction means positioned in said refrigerant bypass tube between said inlet to said refrigerant supply conduit and said check valve adjacent said outdoor heat exchanger, said first and second restriction means restricting the flow of liquid refrigerant through said refrigerant bypass conduit toward said inlet of said refrigerant supply conduit thereby preventing short circuiting of re frigerant around said heat exchanger operating as an evaporator so that liquid refrigerant does not collect in said case.

5. The reversible refrigeration system set forth in claim 4 in which said second refrigerant restriction means in said refri erant bypass tube on the side adjacent said outdoor heat exchanger provides greater restriction than that provided by said first refrigerant restriction means on the side of said refrigerant bypass tube adjacent said indoor heat exchanger.

References (Iited in the file of this patent UNITED STATES PATENTS 2,510,887 Hanson June 6, 1950 2,776,542 Cooper Jan. 8, 1957 2,959,937 Coyne Nov. 15, 1960 2,967,410 Schulze Jan. 10, 1961 

